Commonly wide agricultural implements include right and left wing sections pivotally attached to a center section, such that the wings can be folded upward or rearward for transport. Ground engaging tools such as harrows and packers are commonly mounted on tool bar implements that comprise a center hitch frame that is mounted on center wheels at a rear end thereof and extends forward from the center wheels to a hitch tongue adapted to be attached to the drawbar of a towing vehicle. An elongate center tool bar is pivotally mounted on the rear end of the hitch frame such that its axis is perpendicular to the operating travel direction and right and left elongate wing tool bars are in turn pivotally attached to outer ends of the center tool bar about right and left wing axes and extend outward from there. Cables or like braces are connected between the wing tool bars and the hitch frame to support the outer ends of the wing tool bars. Harrows, packers, or like ground engaging tools are attached to the tool bars.
In one common implement type, when in a field working position the ground engaging tools extend rearward from the tool bars and engage the ground, and the outer ends of the wings are supported on field wheels fixed to the tool bars and oriented to roll in the operating travel direction. The wing axes are aligned with the operating travel direction in the field working position so that outer ends of the wings can move up and down to follow field contours.
When moving from the field to the transport position, an actuator on the hitch frame pivots the center tool bar, and through the pivoting attachment also pivots the right and left wing tool bars such that the ground engaging tools are raised off the ground to an upright orientation and the wing axes are substantially vertical. As the wing tool bars rotate, a transport wheel fixed to each wing tool bar moves down into engagement with the ground to support the wing tool bars, and the field wheels are raised above the ground. The transport wheels are oriented to roll perpendicular to the operating travel direction, and as the hitch frame is towed forward, the wing tool bars pivot with respect to the center tool bar about the now vertical wing axes and move to a trailing orientation substantially aligned with the operating travel direction.
Such implements are disclosed for example in U.S. Pat. No. 4,821,809 to Summach, et al., U.S. Pat. No. 4,418,762 to Page, U.S. Pat. No. 3,640,345 to Sosalla, and U.S. Pat. No. 3,539,016 to Bauer et al. U.S. Pat. No. 2,828,597 to Moore shows a similar implement with a somewhat different arrangement where the same wheel is used for field and for transport.
In the field operating position the rear end of the center hitch frame is supported on the center wheels and the hitch tongue at the front end thereof bears down on the drawbar. As the tool bars rotate, the ground engaging tools are raised up off the ground and the weight of the ground engaging tools is transferred from the ground to the tool bars, which are supported on the outer ends of the wing tool bars by the transport wheels, and by the rear end of the hitch frame. Since the rotational axis of the center tool bar is located on the hitch frame rearward of the rotational axis of the center wheels, when the tool bars rotate the weight of the ground engaging tools exerts a downward force rearward of the center wheel such that an upward force is exerted on the hitch tongue.
Agricultural implements typically include a jack mounted adjacent to the hitch tongue to support the hitch weight when the towing vehicle is disconnected, and to facilitate reconnection. In the tool bar implements for harrows, packers, and the like described above however, when in transport there is negative weight on the hitch tongue and the jack must be mounted on a wing tool bar rearward of the rotational axis of the center wheels to support the weight of the tool bars and ground engaging tools and prevent the upward movement of the hitch tongue and maintain the desired vertical location so that the towing vehicle can easily be reconnected.